I buy alot of Master System games from the UK, and almost always, the sellers ship right away. In fact, I often recieve packages purchased from the UK faster than ones purchased at the same time from US sellers, and the shipping's nearly the same between the two. (usually due to being ripped off on shipping by the US sellers)
Plus, I've never had a UK seller, who's auction stated "ship to UK only", refuse to sell to me after contacting them and asking nicely.